Band pass distributed amplifier



June 21, 1960 G. DE soclo 2,942,201

BAND PASS DISTRIBUTED AMPLIFIER Filed Nov. 10, 1958 INVENTOR. 650365 De 506/0 BY J W HTTOE/YEYS BAND PASS DISTRIBUTED AMPLIFIER George 'de Socio, Baltimore, Md., assignor to the United States of America as represented by the Secretary of the Air Force Filed Nov. 10, 1958, Ser. N0. 713,121

4 Claims. (Cl. 330-54) nited States Fatcnt 2,942,201 Patented June 21, 1960 grid supply line 20 for the incoming signal is constructed r substantially similar to plate line 18 and is constituted by line inductances 68 and capacitors 70 to provide the desired delay between sections. The final or terminal section 12 is provided with a reactor 72 of half the value of the reactors 68, reactors 72 being preferred to ground 6 through a suitable impedance 74.

562, dated July 15, 1936, and discussed in the article entitled Distributed Amplification, appearing in the Proceedings of the I.R.E., vol 36, page 956 (1948), by Ginston, Hewlett, Jasberg and Moe.

The use of the heretofore known distributed amplifier circuits for medium power levels has proven uneconomical and nonefiicient because of the necessityof utilizing high powered tubes in order to realize the required gain. The present invention provides a medium powered level band pass distributed amplifier utilizing conven tioual miniature-tubes. r I

The distributed amplifier according to the invention is constituted by a succession of T-filter sections isolated Other objects and advantages of the invention will be apparent from the following description in which:

Fig. 1 is a schematic diagram of representative stages of a driver band pass distributed amplifier;

Fig. 2 is a simplifier showing of the T-filter configuration of the stage; and

Fig. 3 is a characteristic diagram for the stage. Inthe exemplary embodiment according to the invention the distributed amplifier is constructed of a plurality of T-filter sections, Fig. 1 showing a typical line section 10 and a typical terminal section 12. Obviously, any number of line sections can be assembled to secure the desired power output.

The filter sections 10 and 12 are supplied by a power supply line 14, a grid bias line 16, or a plate line 18 and a grid line 20.

Each filter section is constituted by an inductance 22' coupled to the anodes 24 of a pentode tube 26 by means of the capacitors 28 and 30. Power is supplied from line 14 to the anodes 24 from a power source, not shown, through an inductance 34 having a filter capacitor 36 to ground. Radio frequency chokes 40 are supplied in the line 14 to isolate the sections in the power supply line. A terminal section 12 has the output plate line 18 supplied with an inductance 42 which is of half/the value of the coupling inductance 22. Output terminal 44 isconnected to a load 46 which is returned to ground.

Grids 50of the pentode 26 are supplied with positive potential from a power source through a radio frequency choke 52 and maintained at the desired potential with The construction and operation of this T-filter will be best understood from Fig. 2 showing the simplified T- section and Fig. 3 showing the characteristics of the section.

The utilization and operation of the circuit is easily understood from the calculation of a typical application such as a band pass distributed amplifier having a power output of 8 watts max., a band pass from f of 50 me. to i of 210 me. with a low output impedance of w. In order to provide specific data for calculation a specific tube (Amperex type 6360, twin tetrode) is utilized as an example. However, any similar tube, can be used with its specific data.

Measured values for this tube with both sections connccted in parallel are as follows:

G 7000 umho; input inductance=.02 phenry; input capacitance =l5.5 id; output inductance=.0l7 henry; output capacitance=9.7 i id. (All measurements including socket leads and capacitance.)

The equations for the derivation of the line parameters are well known (for example see Terman, Radio Engineers Handbook) and are as follows:

It is desirable from an operational standpoint to keep w. as high as possible. It was found that the tube lead inductances and capacitances would establish an upper limit to h, or a frequency of 300 me., approximately. The grid elements have the lower resonant frequency. The plate-circuit can be matched for the same 1... provided a high enough Q could be realized. However, this is not the case, and an is of 300 me. for the plate line 18 is assumed, although because of the low Q of the circuit, it is not practical to add the series inductance necessary. It can be shown that the phase velocity of the difierent lines is not materially different, provided f and f are maintained the same. It is not intended to give the impression that this phase error is independent lMA-a za B. Plate line:

C i id. L .0 17 uh. (tube alone) ,;=3oo metre-5,5 h fie- 10c C1k=%-9.7 ira-9.8 id.

L =.s 2 0.24s=0.203 n. L aL .7l 0,2fi8=.0.176 ah. 01:95? ipid. R =125w load resistance of the line necessary for a; matched condition T i Gain calculations The low signal voltage gain of the amplifier tube section is well known, and is:

will gain normalized to the input impedance, we get mH N vF-z To solve for N, set G equal to e the optimum configuration. The minimum number of tubes figures to be 8 tubes. The power capabilities of each tube, however, in

' approximately .7 watt for both sections in parallel. Since the requirement is 8 watts max., at least tubes should be'used. Gain on this'ba'sis is 3.6 or 11 db;

For purpo'se of exemplifi'cation a particular embodiment'has' been shown'and described a'ccordiiigto the best preseneunderstanding thereof. However, it will-be apparent to those'skilled in 'the'art that variouschaiiges and modifications in the'construction andiar'ra'ng'ement 'of the component parts thereof'can be resorted "fowithout 'de} parting from the; true spirit" and scope of the invention.

- "I'cla im 1; Aband pass distributed amplifier comprising a plurality of parallel connecteds'equenti'ally 'op'erati'r'igtubes each'tube including'aplate, a control grid and a cathode, aJco'mrnon powersupply line for'said' tubesfan' individual reactor connecting 'th'elplatejof each tube resets-supply line, each of said cathodes being connected to ground, a capacitor in shunt with each tube and its associated reactor, a radio frequency choke in said supply line between successive tubes, a common bias line for said control grid of each tube, a reactor connecting said bias line-to said control grid in each tube, a capacitor referring said bias to ground for each tube, a radio frequency choke in said bias line between each of said grids, a plate line connected to the plates "of's'aid tubes; saidplate lineincluding a reacaid reactor each of said ine con riect ed to each of said grids, a reactor in said grid line between each grid, a capacitor mend g'rid line 'be'tween eachreactor and the adjacent grids.

2. A band pass distributed amplifier comprising a plurality of parallel connected, sequentially operating sections each of said sections including a plurality of parallel connected dischargeipathsfeach of said discharge paths having alplate," a cathode andat least afirst and a second control grid, a common supply circuit for each of said plates, a'radio frequency-isolatingdevice in said common supply. line between each ofi said plurality of parallel connct'ed discharge pa th's, a reactor connected in series between the'discharge paths of each section and said supply circuit, a capacitor connected in shunt with said reactor and thedischarge paths in series therewith, a common bias circuit for said firstcontrol grid in each of said dis charge paths, a radio frequency-isolating device in said bias circuit between eachof said sections, a plate line connected to the plates of each of said secti'ons, said plate line including a reactor in series between each of said sectionsfand a capacitor in series circuit relation between eachofi said plate line reactors and the adjacent discharge paths, a grid line connected to said first control electrbdes'a reactor in said gridline between each of said sections andl-a capacitor in said grid line between each of said grid line reactors and each adjacent first grid.

3-. A bandpass distributed amplifier comprising a plurality of parallel connected, sequentially operating sec tion's; each of said sections including a plurality of parallel'connected discharge paths, each ofsaid discharge paths having a plate, acathode and at least a first and a second control grid, a common supply circuit for each of said plates, a radio frequency isolating device in said common supply line'betwe'en each ofsaid plurality of parallelconnecteddischarge. paths a reactor connected in series between thedischai'ge paths ofeach section and said, supply circuit, a capacitor connected in shunt-with said reactor and the discharge paths in series therewith, a common: bias circuit for,said first control grid in each of 'said discharge paths, a radio frequency-isolating device in said bias" circuit between each ofsaid sections, a plate line conneted to, the plates of each ofsaid sections, said plate- 'line including a reactorin series between each of said-sections, and a capacitor in said plate line in series circuit relation between each of said plate linereactors a-nd the adjacenndischarge paths a grid line connected to said first control electrodes, a reactor in saidgrid; line between eachof said sections and a capacitor in said grid line between each of said-gridli ne reactors and each adjacent grid, a second common bias line connected to said second 'grids, a radio frequency-isolating. device in said-second line between each section.

4, A band pass distributed amplifier comprisinga plurality ofaparalle l connected; sequentially 'opergating secti'on's each-of said's ectionsincluding a plurality of'paralll "connected discharge paths, each of said discharge paths liaving' a'plate,"'a cathodeandatleasta first and a second control grid, a coinmon supply circuit for each of-"said plates, a jradioi frequency-isolating device iii-said commonfs'upply line between each" of said plur ality or parallelj conrieoted {discharge paths, a reactor connected in .seri'esibetw'een the discharge paths ofeach sectionand sal ensure: a capacitor cdnpelc t ed inshunt said reactor and the discharge paths in series therewith, a

common bias circuit for said first control grid in each of said discharge paths, a radio frequency-isolating device in said bias circuit between each of said sections, at capacitor connected between said bias line and ground in each section, a reactor connected between said bias line and the first grids of each section, a plate line connected to the plates of each of said sections, said plate line in cluding a reactor in series between each of said sections, and a capacitor in a series circuit relation in said plate line between each of said plate line reactors and the adjacent discharge paths, a grid line connected to said first control electrodes, a reactor in said grid line between each of said sections and a capacitor in said grid line between each of said grid line reactors and each adjacent first grid.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Publication, Electronics, July, 1951, pages 106-l11, Millimicrosecond Oscillography, by Y. P. Yu et a1. 

